7-(Pyrimidin-4-yl)-Imidazo[1,2-a]Pyrimidin-5(1H)-ones as GSK3β inhibitors

ABSTRACT

The invention relates to a imidazo[1,2-a]pyrimidone derivative represented by formula (I) or a salt thereof: R 1  wherein X represents a bond, an ethenylene group, an ethenylene group, a methylene group optionally substituted; a carbonyl group, an oxygen atom, a sulfur atom, a sulfonyl group, a sulfoxide group or a nitrogen atom being optionally substituted; R 1  represents a 2, 4 or 5-pyrimidinyl optionally substituted; R 2  represents a C 1-6  alkyl group, a C 1-2  perhalogenated alkyl group,a C 1-3  halogenated alkyl group, a benzyl group, a benzene ring, a naphthalene ring, 5,6,7,8-tetrahydronaphthalene ring, a pyridine ring, an indole ring, a pyrrole ring, a thiophene ring, a furan ring or an imidazole ring, the benzyl group and the rings being optionally substituted; and n represents 0 to 3. The invention relates also to a medicament comprising the said derivative or a salt thereof as an active ingredient which is used for preventive and/or therapeutic treatment of a neurodegenerative disease caused by abnormal activity of GSK3β, such as Alzheimer disease.

TECHNICAL FIELD

The present invention relates to compounds that are useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of neurodegenerative diseases caused by abnormal activity of GSK3β.

BACKGROUND ART

GSK3β (glycogen synthase kinase 3β) is a proline directed serine, threonine kinase that plays an important role in the control of metabolism, differentiation and survival. It was initially identified as an enzyme able to phosphorylate and hence inhibit glycogen synthase. It was later recognised that GSK3β was identical to tau protein kinase 1 (TPK1), an enzyme that phosphorylates tau protein in epitopes that are also found to be hyperphosphorylated in Alzheimer's disease and in several taupathies. Interestingly, protein kinase B (AKT) phosphorylation of GSK3β results in a loss of its kinase activity, and it has been hypothesised that this inhibition may mediate some of the effects of neurotrophic factors. Moreover, phosphorylation by GSK3β of β-catenin, a protein involved in cell survival, results in its degradation by an ubiquitinilation dependent proteasome pathway.

Thus, it appears that inhibition of GSK3β activity may result in neurotrophic activity. Indeed there is evidence that lithium, an uncompetitive inhibitor of GSK3β, enhances neuritogenesis in some models and also increases neuronal survival, through the induction of survival factors such as Bcl-2 and the inhibition of the expression of proapoptotic factors such as P53 and Bax.

Recent studies have demonstrated that β-amyloid increases the GSK3β activity and tau protein phosphorylation. Moreover, this hyperphosphorylation as well as the neurotoxic effects of β-amyloid are blocked by lithium chloride and by a GSK3β antisense mRNA. These observations strongly suggest that GSK3β may be the link between the two major pathological processes in Alzheimer's disease: abnormal APP (Amyloid Precursor Protein) processing and tau protein hyperphosphorylation.

Although tau hyperphosphorylation results in a destabilisation of the neuronal cytoskeleton, the pathological consequences of abnormal GSK3β activity are, most likely, not only due to a pathological phosphorylation of tau protein because, as mentioned above, an excessive activity of this kinase may affect survival through the modulation of the expression of apoptotic and antiapoptotic factors. Moreover, it has been shown that β-amyloid-induced increase in GSK3β activity results in the phosphorylation and, hence the inhibition of pyruvate dehydrogenase, a pivotal enzyme in energy production and acetylcholine synthesis.

Altogether these experimental observations indicate that GSK3β may find application in the treatment of the neuropathological consequences and the cognitive and attention deficits associated with Alzheimer's disease, as well as other acute and chronic neurodegenerative diseases. These include, in a non-limiting manner, Parkinson's disease, tauopathies (e.g. frontotemporoparietal dementia, corticobasal degeneration, Pick's disease, progressive supranuclear palsy) and other dementia including vascular dementia; acute stroke and others traumatic injuries; cerebrovascular accidents (e.g. age related macular degeneration); brain and spinal cord trauma; peripheral neuropathies; retinopathies and glaucoma.

In addition GSK3β may find application in the treatment of other diseases such as: Non-insulin dependent diabetes (such as diabetes type II) and obesity; manic depressive illness; schizophrenia; alopecia; cancers such as breast cancer, non-small cell lung carcinoma, thyroid cancer, T or B-cell leukemia and several virus-induced tumors.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide compounds useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of a disease caused by abnormal GSK3β activity, more particularly of neurodegenerative diseases. More specifically, the object is to provide novel compounds useful as an active ingredient of a medicament that enables prevention and/or treatment of neurodegenerative diseases such as Alzheimer's disease.

Thus, the inventors of the present invention have identified compounds possessing inhibitory activity against GSK3β. As a result, they found that compounds represented by the following formula (I) had the desired activity and were useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of the aforementioned diseases.

The present invention thus provides imidazo[1,2-a]pyrimidone derivatives represented by formula (I) or salts thereof, solvates thereof or hydrates thereof:

wherein:

-   X represents a bond, an ethenylene group, an ethynylene group, a     methylene group optionally substituted by one or two groups selected     from a C₁₋₆ alkyl group, a hydroxy group and a C₁₋₄ alkoxy group; a     carbonyl group, an oxygen atom, a sulfur atom, a sulfonyl group, a     sulfoxide group or a nitrogen atom being optionally substituted by a     C₁₋₆ alkyl group; -   R1 represents a 2, 4 or 5-pyrimidine ring optionally substituted by     a C₁₄ alkyl group, C₁₋₄ alkoxy group or a halogen atom; -   R2 represents a C₁₋₆ alkyl group, a C₁₋₂ perhalogenated alkyl group,     a C₁₋₃ halogenated alkyl group, a benzyl group, a benzene ring, a     naphthalene ring, 5,6,7,8-tetrahydronaphthalene ring, a pyridine     ring, an indole ring, a pyrrole ring, a thiophene ring, a furan ring     or an imidazole ring, the benzyl group and the rings being     optionally substituted by 1 to 4 substituents selected from a C₁₋₆     alkyl group, a benzene ring, a halogen atom, a C₁₋₂ perhalogenated     alkyl group, a C₁₋₃ halogenated alkyl group, a hydroxyl group, a     C₁₋₄ alkoxy group, a nitro, a cyano, an amino, a C₁₋₆ monoalkylamino     group or a C₂₋₁₀ dialkylamino group; -   and n represents 0 to 3.

According to another aspect of the present invention, there is provided a medicament comprising as an active ingredient a substance selected from the group consisting of the pyrimidone derivatives represented by formula (I) and the physiologically acceptable salts thereof, and the solvates thereof and the hydrates thereof. As preferred embodiments of the medicament, there are provided the aforementioned medicament which is used for preventive and/or therapeutic treatment of diseases caused by abnormal GSK3β activity, and the aforementioned medicament which is used for preventive and/or therapeutic treatment of neurodegenerative diseases and in addition other diseases such as: Non-insulin dependent diabetes (such as diabetes type II) and obesity; manic depressive illness; schizophrenia; alopecia; cancers such as breast cancer, non-small cell lung carcinoma, thyroid cancer, T or B-cell leukemia and several virus-induced tumors.

As further preferred embodiments of the present invention, there are provided the aforementioned medicament wherein the diseases are neurodegenerative diseases and are selected from the group consisting of Alzheimer's disease, Parkinson's disease, tauopathies (e.g. frontotemporoparietal dementia, corticobasal degeneration, Pick's disease, progressive supranuclear palsy) and other dementia including vascular dementia; acute stroke and others traumatic injuries; cerebrovascular accidents (e.g. age related macular degeneration); brain and spinal cord trauma; peripheral neuropathies; retinopathies and glaucoma, and the aforementioned medicament in the form of pharmaceutical composition containing the above substance as an active ingredient together with one or more pharmaceutical additives.

The present invention further provides an inhibitor of GSK3β activity comprising as an active ingredient a substance selected from the group consisting of the imidazo[1,2-a]pyrimidone derivatives of formula (I) and the salts thereof, and the solvates thereof and the hydrates thereof.

According to further aspects of the present invention, there is provided a method for preventive and/or therapeutic treatment of neurodegenerative diseases caused by abnormal GSK3β activity, which comprises the step of administering to a patient a preventively and/or therapeutically effective amount of a substance selected from the group consisting of the imidazo[1,2-a]pyrimidone derivatives of formula (I) and the physiologically acceptable salts thereof, and the solvates thereof and the hydrates thereof; and a use of a substance selected from the group consisting of the imidazo[1,2-a]pyrimidone derivatives of formula (I) and the physiologically acceptable salts thereof, and the solvates thereof and the hydrates thereof for the manufacture of the aforementioned medicament.

As used herein, the C₁₋₆ alkyl group represents a straight or branched alkyl group having 1 to 6 carbon atoms, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, 1,1-dimethylpropyl group, n-hexyl group, isohexyl group, and the like;

The C₁₋₄ alkoxy group represents an alkyloxy group having 1 to 4 carbon atoms for example, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, and the like;

The halogen atom represents a fluorine, chlorine, bromine or iodine atom; The C₁₋₂ perhalogenated alkyl group represents an alkyl group wherein all the hydrogen have been substituted by a halogen atom, for example a CF₃ or C₂F₅;

The C₁₋₃ halogenated alkyl group represents an alkyl group wherein at least one hydrogen has not been substituted by an halogen atom;

The C₁₋₆ monoalkylamino group represents an amino group substituted by one C₁₋₆ alkyl group, for example, methylamino group, ethylamino group, propylamino group, isopropylamino group, butylamino group, isobutylamino group, tert-butylamino group, pentylamino group and isopentylamino group;

The C₂₋₁₀ dialkylamino group represents an amino group substituted by two C₁₋₅ alkyl groups, for example, dimethylamino group, ethylmethylamino group, diethylamino group, methylpropylamino group and diisopropylamino group;

The methylene group represents a divalent group of formula: —CH₂—

The ethenylene group represents the divalent group of formula:

The ethynylene group represents the divalent group of formula:

The leaving group represents a group which could be easily cleaved and substituted, such a group may be for example a tosyloxy, a mesyloxy, a bromide and the like.

The compounds represented by the aforementioned formula (I) may form a salt. Examples of the salt include, when an acidic group exists, salts of alkali metals and alkaline earth metals such as lithium, sodium, potassium, magnesium, and calcium; salts of ammonia and amines such as methylamine, dimethylamine, trimethylamine, dicyclohexylamine, tris(hydroxymethyl)aminomethane, N,N-bis(hydroxyethyl)piperazine, 2-amino-2-methyl-1-propanol, ethanolamine, N-methylglucamine, and L-glucamine; or salts with basic amino acids such as lysine, δ-hydroxylysine, and arginine. The base-addition salts of acidic compounds are prepared by standard procedures well known in the art.

When a basic group exists, examples include salts with mineral acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid; salts with organic acids such as methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, acetic acid, propionic acid, tartaric acid, fumaric acid, maleic acid, malic acid, oxalic acid, succinic acid, citric acid, benzoic acid, mandelic acid, cinnamic acid, lactic acid, glycolic acid, glucuronic acid, ascorbic acid, nicotinic acid, and salicylic acid; or salts with acidic amino acids such as aspartic acid, and glutamic acid.

The acid-addition salts of the basic compounds are prepared by standard procedures well know in the art which include, but are not limited thereto, dissolving the free base in an aqueous alcohol solution containing the appropriate acid and isolating the salt by evaporating the solution, or by reacting the free base and an acid in an organic solvent, in which case the salt separates directly, or is precipitated with a second organic solvent, or can be obtained by concentration of the solution. The acids which can be used to prepare the acid-addition salts include preferably those which produce, when combined with the free base, pharmaceutically-acceptable salts, that is, salts whose anions are relatively innocuous to the animal organism in pharmaceutical doses of the salts, so that the beneficial properties inherent in the free base are not compromised by side effects ascribable to the anions. Although medicinally acceptable salts of the basic compounds are preferred, all acid-addition salts are within the scope of the present invention.

In addition to the imidazo[1,2-a]pyrimidone derivatives represented by the aforementioned formula (I) and salts thereof, their solvates and hydrates also fall within the scope of the present invention. The imidazo[1,2-a]pyrimidone derivatives represented by the aforementioned formula (I) may have one or more asymmetric carbon atoms. As for the stereochemistry of such asymmetric carbon atoms, they may independently be in either (R) and (S) configuration, and the imidazo[1,2-a]pyrimidone derivative may exist as stereoisomers such as optical isomers, or diastereoisomers. Any stereoisomers in pure form, any mixtures of stereoisomers, racemates and the like fall within the scope of the present invention.

Examples of preferred compounds of the present invention are shown in table 1 hereinafter. However, the scope of the present invention is not limited by these compounds.

Preferred compounds of the present invention represented by formula (I) include also:

-   (1) Compounds wherein R1 represents a 4 or 5-pyrimidine ring and     more preferably a 4-pyrimidine ring, which may be substituted by a     C₁₋₂ alkyl group, a C₁₋₂ alkoxy group or a halogen atom; and/or -   (2) X represents a bond, a methylene group optionally substituted or     a carbonyl group.

More preferred compounds of the present invention represented by formula (I) include also:

-   (1) Compounds wherein R1 represents an unsubstituted 4-pyrimidine     ring; and/or -   (2) Compounds wherein R2 represents a benzene ring, a naphthalene     ring or a 5,6,7,8-tetrahydronaphthalene ring; more preferably a     benzene ring or a naphthalene ring; the rings being optionally     substituted; and/or -   (3) Compounds wherein X represents an unsubstituted methylene group     or a carbonyl group.

Particularly preferred compounds of the present invention represented by formula (I) include:

-   1     1-(3-Phenyl-propyl)-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   2     1-[3-(2-Fluoro-phenyl)-propyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   3     1-[2-(4-Fluoro-2-methoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   4     1-[2-(4-Methoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   5     1-[2-(4-Methyl-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   6     1-(2-Naphthalen-1-yl-ethyl)-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   7     1-[2-(3-Fluoro-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   8     1-[2-(3-Chloro-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   9     1-[2-(2-Methoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   10     4-[2-(5-Oxo-7-(pyrimidin-4-yl)-5H-imidazo[1,2-a]pyrimidin-1-yl)-ethyl]-benzonitrile -   11     1-(2-Hydroxy-2-phenyl-ethyl)-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   12     1-(2-Oxo-2-phenyl-ethyl)-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   13     1-[2-(4-Fluoro-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   14     1-[2-(4-Ethoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one -   15     1-[2-(2,5-Dimethoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one.

As a further object, the present invention concerns also methods for preparing the imidazo[1,2-a]pyrimidone compounds represented by the aforementioned formula (I).

These compounds can be prepared, for example, according to methods explained below.

Preparation Method

Imidazo[1,2-a]pyrimidone compounds represented by the aforementioned formula (I) may be prepared according to scheme 1.

(In the above scheme the definition of R1, R2, X and n are the same as those already described for compound of formula (I)).

The 7-(pyrimidinyl)-imidazo[1,2-a]pyrimidin-5(1H)-one derivative represented by the above formula (III), wherein R1 is as defined for compound of formula (I), is allowed to react with a base such as sodium hydride, sodium carbonate or potassium carbonate in a solvent such as N,N-dimethylformamide, N-methylpyrrolidine, N,N-dimethylacetamide or chloroform at a suitable temperature ranging from 0 to 130° C. under ordinary air, then with a compound of formula (II), wherein R2, X and n are as defined for compound of formula (I) and L represents a leaving group preferably bromide or mesyloxy group, is added to obtain the compound of the aforementioned formula (I).

Compound of formula (II) are commercially available or may be synthesised according to well-known methods of one skilled in the art. The compound of formula (III) may be prepared according to the method defined in scheme 2.

(In the above scheme the definition of R1 is the same as already described.)

According to this method, the 3-ketoester of formula (V), wherein R represents an alkyl group such as for example a methyl or ethyl group, is allowed to react with a 2-aminoimidazole of formula (IV). The reaction may be carried out in the presence of an ammonium salt such as ammonium,acetate, in a alcoholic solvent such as methanol, ethanol and the like or without, at a suitable temperature ranging from 25°-140° C. under ordinary air.

Compound of formula (IV) is commercially available, compound of formula (V) may be synthesised by analogy to the method described in patent DE2705582.

For example compounds of formula (V), wherein R1 represent a pyrimidine ring. optionally substituted by a C₁₋₄ alkyl group, C₁₋₄ alkoxy group or a halogen atom, can be prepared by reacting a pyrimidinyl-4-carboxylic acid optionally substituted by a C₁₋₄ alkyl group, C₁₋₄ alkoxy group or an halogen, with a malonic acid monoester. The reaction can be carried out using methods well known to one skilled in the art, such as for example in presence of a coupling agent such as 1,1′-carbonylbis-1H-imidazole in a solvent such as tetrahydrofuran at a temperature ranging from 20 to 70° C.

In the above reactions, protection or deprotection of a functional group may sometimes be necessary. A suitable protecting group Pg can be chosen depending on the type of the functional group, and a method described in the literature may be applied. Examples of protecting groups, of protection and deprotection methods are given for example in Protective groups in Organic Synthesis Greene et al., 2nd Ed. (John Wiley & Sons, Inc., New York).

The compounds of the present invention have inhibitory activity against GSK3β. Accordingly, the compounds of the present invention are useful as an active ingredient for the preparation of a medicament, which enables preventive and/or therapeutic treatment of a disease caused by abnormal GSK3β activity and more particularly of neurodegenerative diseases such as Alzheimer's disease. In addition, the compounds of the present invention are also useful as an active ingredient for the preparation of a medicament for preventive and/or therapeutic treatment of neurodegenerative diseases such as Parkinson's disease, tauopathies (e.g. frontotemporoparietal dementia, corticobasal degeneration, Pick's disease, progressive supranuclear palsy) and other dementia including vascular dementia; acute stroke and others traumatic injuries; cerebrovascular accidents (e.g. age related macular degeneration); brain and spinal cord trauma; peripheral neuropathies; retinopathies and glaucoma; and other diseases such as non-insulin dependent diabetes (such as diabetes type II) and obesity; manic depressive illness; schizophrenia; alopecia; cancers such as breast cancer, non-small cell lung carcinoma, thyroid cancer, T or B-cell leukemia and several virus-induced tumors.

The present invention further relates to a method for treating neurodegenerative diseases caused by abnormal activity of GSK3β and of the aforementioned diseases which comprises administering to a mammalian organism in need thereof an effective amount of a compound of the formula (I).

As the active ingredient of the medicament of the present invention, a substance may be used which is selected from the group consisting of the compound represented by the aforementioned formula (I) and pharmacologically acceptable salts thereof, and solvates thereof and hydrates thereof. The substance, per se, may be administered as the medicament of the present invention, however, it is desirable to administer the medicament in a form of a pharmaceutical composition which comprises the aforementioned substance as an active ingredient and one or more pharmaceutical additives. As the active ingredient of the medicament of the present invention, two or more of the aforementioned substances may be used in combination. The above pharmaceutical composition may be supplemented with an active ingredient of another medicament for the treatment of the above mentioned diseases. The type of pharmaceutical composition is not particularly limited, and the composition may be provided as any formulation for oral or parenteral administration. For example, the pharmaceutical composition may be formulated, for example, in the form of pharmaceutical compositions for oral administration such as granules, fine granules, powders, hard capsules, soft capsules, syrups, emulsions, suspensions, solutions and the like, or in the form of pharmaceutical compositions for parenteral administrations such as injections for intravenous, intramuscular, or subcutaneous administration, drip infusions, transdermal preparations, transmucosal preparations, nasal drops, inhalants, suppositories and the like. Injections or drip infusions may be prepared as powdery preparations such as in the form of lyophilised preparations, and may be used by dissolving just before use in an appropriate aqueous medium such as physiological saline. Sustained-release preparations such as those coated with a polymer may be directly administered intracerebrally.

Types of pharmaceutical additives used for the manufacture of the pharmaceutical composition, content ratios of the pharmaceutical additives relative to the active ingredient, and methods for preparing the pharmaceutical composition may be appropriately chosen by those skilled in the art. Inorganic or organic substances, or solid or liquid substances may be used as pharmaceutical additives. Generally, the pharmaceutical additives may be incorporated in a ratio ranging from 1% by weight to 90% by weight based on the weight of an active ingredient.

Examples of excipients used for the preparation of solid pharmaceutical compositions include, for example, lactose, sucrose, starch, talc, cellulose, dextrin, kaolin, calcium carbonate and the like. For the preparation of liquid compositions for oral administration, a conventional inert diluent such as water or a vegetable oil may be used. The liquid composition may contain, in addition to the inert diluent, auxiliaries such as moistening agents, suspension aids, sweeteners, aromatics, colorants, and preservatives. The liquid composition may be filled in capsules made of an absorbable material such as gelatin. Examples of solvents or suspension mediums used for the preparation of compositions for parenteral administration, e.g. injections, suppositories, include water, propylene glycol, polyethylene glycol, benzyl alcohol, ethyl oleate, lecithin and the like. Examples of base materials used for suppositories include, for example, cacao butter, emulsified cacao butter, lauric lipid, witepsol.

The dose and frequency of administration of the medicament of the present invention are not particularly limited, and they may be appropriately chosen depending on conditions such as a purpose of preventive and/or therapeutic treatment, a type of a disease, the body weight or age of a patient, severity of a disease and the like. Generally, a daily dose for oral administration to an adult may be 0.01 to 1,000 mg (the weight of an active ingredient), and the dose may be administered once a day or several times a day as divided portions, or once in several days. When the medicament is used as an injection, administrations may preferably be performed continuously or intermittently in a daily dose of 0.001 to 100 mg (the weight of an active ingredient) to an adult.

CHEMICAL EXAMPLES

The present invention will be explained more specifically with reference to the following general examples, however, the scope of the present invention is not limited to these examples.

Example 1 Compound No 2 of table 1 1-[3-(2-Fluoro-phenyl)-propyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one hydrochloride (1:1) 1.1. 7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one

A mixture containing 2.9 g (15 mmol) of 3-oxo-3-(pyrimidin-4-yl)-propionic acid ethyl ester (prepared by analogy to the method described in patent DE 2705582), 2 g (15 mmol) of 2-aminoimidazole hemisulfate and 1.2 g (15 mmol) of ammonium acetate was heated at 140° C. during 18 h.

The cooled mixture was treated with 30 ml of acetonitrile and filtered and the precipitate was added to water and heated at reflux temperature for 30 min.

The resulting solution was cooled and the precipitate recovered by filtration. The crude product thus obtained was recrystallised from ethanol to give 1.75 g of pure product as a gray solid.

Mp: 345-346° C.

1.2. 1-[3-(2-Fluoro-phenyl)-propyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one hydrochloride (1:1)

A suspension of 0.433 g (2.03 mmol) of 7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one in 4 ml of anhydrous N,N-dimethylformamide was treated with 365 mg (2.64 mmol) of potassium carbonate and the resulting mixture was heated at 70° C. for 30 min. 530 mg (2.44 mmol) of 3-(2-fluoro-phenyl)propyl bromide was added and the reaction mixture was heated at 130° C. during 1 h.

The cooled solution was treated with water and extracted with ethyl acetate. The organic phase was dried and evaporated to give crude product which was purified by silica gel chromatography, eluting with dichloromethane/methanol in the proportions 100/0 to 95/5. There is obtained 0.248 g of pure product in the form of the free base which was transformed into the hydrochloride salt.

Mp: 192-194° C.

Example 2 Compound No 3 of table 1 1-[2-(4-Fluoro-2-methoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one 2.1 (4-Fluoro-2-methoxy-phenyl)-acetic acid methyl ester

To a suspension of 14.34 g (32.47 mmol) of lead (IV) acetate in 100 ml of anhydrous toluene was added a mixture of 5.2 g (30.92 mmol) of 1-(4-fluoro-2-methoxy-phenyl)-ethanone and 15.02 ml (123.13 mmol) of boron trifluoride etherate in 9 ml of methanol. The reaction mixture is further stirred at room temperature for 16 h. Water was added to the cooled mixture and the resulting solution extracted with toluene. The extracts were washed with saturated sodium hydrogen carbonate solution, saturated sodium chloride solution and dried with sodium sulphate. The solvent was evaporated to dryness to give 6 g of product as an oil which was used in the subsequent step without further purification.

2.2 2-(4-Fluoro-2-methoxy-phenyl)-ethanol

To a suspension of 1.72 g ( 45.41 mmol) of lithium aluminium hydride in 120 ml of tetrahydrofuran at 0° C. was added dropwise 6 g (30.27 mmol) of dissolved in 120 ml of (4-fluoro-2-methoxy-phenyl)-acetic acid methyl ester and the resulting mixture stirred at room temperature for 1 h.

The reaction mixture was diluted with 100 ml of diethylether at 0° C. and treated with excess of a saturated aqueous solution of sodium sulphate. Further solid sodium sulphate was added and the organic phase was filtered to remove salts. The solvent was evaporated to dryness to give 5.1 g (99%) of product as an oil.

2.3 Methanesulfonic acid 2-(4-fluoro-2-methoxy-phenyl)-ethyl ester

To a solution of 5.1 g (29.97 mmol) of 2-(4-fluoro-2-methoxy-phenyl)-ethanol in 30 ml of anhydrous dichloromethane was added at 0° C. 6.26 ml (44.95 mmol) of triethylamine and 3.5 ml (44.95 mmol) of methanesulfonyl chloride.

The resulting mixture was stirred at 0° C. for 1 h. The mixture was then diluted with water and dichloromethane and extracted with dichloromethane. Organic layer was dried and evaporated to give 7 g (100%) of methanesulfonic acid 2-(4-fluoro-2-methoxy-phenyl)-ethyl ester.

2.4 1-[2-(4-Fluoro-2-methoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one

A suspension of 0.4 g (1.88 mmol) of 7-(pyrimidin-4-yl)-1H-imidazo[1,2-a]pyrimidin-5-one in 10 ml of anhydrous N,N-dimethylformamide was treated with 337 mg (2.44 mmol) of potassium carbonate and the resulting mixture was heated at 70° C. for 30 min. 605 mg (2.44 mmol) of methanesulfonic acid 2-(4-fluoro-2-methoxy-phenyl)-ethyl ester was added and the reaction mixture was heated at 80° C. during 16 h.

The cooled solution was treated with waters and extracted with ethyl acetate. The organic phase was dried and evaporated to give crude product which was purified by silica gel chromatography, eluting with dichloromethane/methanol in the proportions 100/0 to 95/5. There is obtained 0.12 g of pure product in the form of the free base.

Mp: 196-198° C.

A list of chemical structures and physical data for compounds of the aforementioned formula (I) illustrating the present invention is given in table 1. The compounds have been prepared according to the methods of the example.

In the table, R1 is an unsubstituted 4-pyrimidine ring Ph represents a phenyl group, (S) indicates the stereochemistry of the carbon atom, and

in the structure of R2 represents the bond attached to X.

TABLE 1

N^(o) X R2 n Mp ° C. salt 1 CH₂ Ph 2 165-170 (1:1) hydrochloride 2 CH₂

2 192-194 (1:1) hydrochloride 3 CH₂

1 196-198 Free base 4 CH₂

1 160-162 Free base 5 CH₂

1 186-188 Free base 6 CH₂

1 215-217 Free base 7 CH₂

1 160-162 Free base 8 CH₂

1 152-154 Free base 9 CH₂

1 160-162 Free base 10 CH₂

1 232-234 Free base 11 CH(OH)(S) Ph 1 159-161 Free base 12 CO Ph 1 240-242 Free base 13 CH₂

1 145-147 Free base 14 CH₂

1 194-196 Free base 15 CH₂

1 155-157 Free base

Test Example Inhibitory Activity of the Medicament of the Present Invention Against GSK3β

Two different protocols can be used.

In a first protocol : 7.5 μM of prephosphorylated GS1 peptide and 10 μM ATP (containing 300,000 cpm of 33P-ATP) were incubated in 25 mM Tris-HCl, pH 7.5, 0.6 mM DTT, 6 mM MgCl₂, 0.6 mM EGTA, 0.05 mg/ml BSA buffer for 1 hour at room temperature in the presence of GSK3β (total reaction volume : 100 microliters).

In a second protocol : 4.1 μM of prephosphorylated GS1 peptide and 42 μM ATP (containing 260,000 cpm 33P-ATP) were incubated in 80 mM Mes-NaOH, pH 6.5, 1 mM Mg acetate, 0.5 mM EGTA, 5 mM 2-mercaptoethanol, 0.02% Tween 20, 10% glycerol buffer for 2 hours at room temperature in the presence of GSK3β. Inhibitors were solubilised in DMSO (final solvent concentration in the reaction medium, 1%).

The reaction was stopped with 100 microliters of a solution made of 25 g polyphosphoric acid (85% P₂O₅), 126 ml 85% H₃PO₄, H₂O to 500 ml and then diluted to 1:100 before use. An aliquot of the reaction mixture was then transferred to Whatman P81 cation exchange filters and rinsed with the solution described above. Incorporated 33P radioactivity was determined by liquid scintillation spectrometry.

The phosphorylated GS-1 peptide had the following sequence: NH2-YRRAAVPPSPSLSRHSSPHQS(P)EDEE-COOH.

The GSK3β inhibitory activity of the compounds of the present invention are expressed in IC₅₀, and as an illustration the range of IC₅₀'s of the compounds in table 1 is between 20 nanomolar to 1 micromolar concentrations.

As for example compound No. 6 of table 1 shows an IC₅₀ of 21 nM.

Formulation Example

(1) Tablets

The ingredients below were mixed by an ordinary method and compressed by using a conventional apparatus.

Compound of Example 1  30 mg Crystalline cellulose  60 mg Corn starch 100 mg Lactose 200 mg Magnesium stearate  4 mg (2) Soft Capsules

The ingredients below were mixed by an ordinary method and filled in soft capsules.

Compound of Example 1  30 mg Olive oil 300 mg Lecithin  20 mg (1) Parenteral Preparations

The ingredients below were mixed by an ordinary method to prepare injections contained in a 1 ml ampoule.

Compound of Example 1 3 mg Sodium chloride 4 mg Distilled water for injection 1 ml

INDUSTRIAL APPLICABILITY

The compounds of the present invention have GSK3β inhibitory activity and are useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of diseases caused by abnormal activity of GSK3β and more particularly of neurodegenerative diseases. 

1. A compound of formula (I) or a pharmaceutically acceptable salt thereof:

wherein: X represents a covalent single bond, an ethenylene group, an ethynylene group, a methylene group optionally substituted by one or two groups selected from a C₁₋₆ alkyl group, a hydroxy group and a C₁₋₄ alkoxy group; a carbonyl group, an oxygen atom, a sulfur atom, a sulfonyl group, a sulfoxide group or a nitrogen atom being optionally substituted by a C₁₋₆ alkyl group; R₁ represents a 2, 4 or 5-pyrimidinyl optionally substituted by a C₁₋₄ alkyl group, C₁₋₄ alkoxy group or a halogen atom; R₂ represents a C₁₋₆ alkyl group, a C₁₋₂ perhalogenated alkyl group, a C₁₋₃ halogenated alkyl group, a benzyl group, a benzene ring, a naphthalene ring, 5,6,7,8-tetrahydronaphthalene ring, a pyridine ring, an indole ring, a pyrrole ring, a thiophene ring, a furan ring or an imidazole ring, the benzyl group and the rings being optionally substituted by 1 to 4 substituents selected from a C₁₋₆ alkyl group, a benzene ring, a halogen atom, a C₁₋₂ perhalogenated alkyl group, a C₁₋₃ halogenated alkyl group, a hydroxyl group, a C₁₋₄ alkoxy group, a nitro, a cyano, an amino, a C₁₋₆ monoalkylamino group or a C₂₋₁₀ dialkylamino group; and n represents 0 to
 3. 2. The compound of formula (I) according to claim 1, wherein R₁ represents an unsubstituted 4-pyrimidine ring.
 3. The compound of formula (I) according to claim 1, wherein R₂ is a benzene ring, a naphthalene ring, or a 5,6,7,8-tetrahydronaphthalene ring, the rings being optionally substituted by 1 to 4 substituents selected from a C₁₋₆ alkyl group, a benzene ring, a halogen atom, a C₁₋₂ perhalogenated alkyl group, a C₁₋₃ halogenated alkyl group, a hydroxyl group, a C₁₋₄ alkoxy group, a nitro, a cyano, an amino, a C₁₋₆ monoalkylamino group or a C₂₋₁₀ dialkylamino group.
 4. A compound selected from the group consisting of: 1-(3-Phenyl-propyl)-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[3-(2-Fluoro-phenyl)-propyl]-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2-(4-Fluoro-2-methoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl )-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2-(4-Methoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2-(4-methyl-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-(2-Naphthalen-1-yl-ethyl)-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2(3-Fluoro-phenyl)-ethyl]7-(pyrimidin-4yl )-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2-(3-Chloro-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2-(2-Methoxy-phenyl)-ethyl]7-(pyrimidin4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 4-[2-[5-Oxo-7-(pyrimidin-4-yl)-5H-imidazo[1,2-a]pyrimidin-1-yl]-ethyl]-benzonitrile; 1-(2-Hydroxy-2phenylethyl)-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-(2-Oxo-2-phenyl-ethyl)-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2(4-Fluoro-phenyl)-ethyl]-7-(pyrimidin4yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; 1-[2-(4-Ethoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; and 1-[2-(2,5-Dimethoxy-phenyl)-ethyl]-7-(pyrimidin-4-yl)-1 H-imidazo[1,2-a]pyrimidin-5-one; or a pharmaceutically acceptable salt thereof.
 5. A compound of formula (III):

wherein: R₁ represents a 2, 4 or 5-pyrimidinyl optionally substituted by a C₁₋₄ alkyl group, C₁₋₄ alkoxy group or a halogen atom.
 6. The compound of formula (I) according to claim 2, wherein R₂ is a benzene ring, a naphthalene ring, or a 5,6,7,8-tetrahydronaphthalene ring, the rings being optionally substituted by 1 to 4 substituents selected from a C₁₋₆ alkyl group, a benzene ring, a halogen atom, a C₁₋₂ perhalogenated alkyl group, a C₁₋₃ halogenated alkyl group, a hydroxyl group, a C₁₋₄ alkoxy group, a nitro, a cyano, an amino, a C₁₋₆ monoalkylamino group or a C₂₋₁₀ dialkylamino group. 